DESCRIPTION (applicant's abstract): Autologous hematopoietic stem cell (HSC) transplantation is used for treatment of many cancers. However, contaminating tumor cells within HSC harvests are problematic since their contribution to disease relapse has been unambigiously established through gene-marking studies. Therefore, technology that reliably eliminates detectable tumor cells, while leaving HSCs undamaged, is needed. Several purging methods have been developed, but they are known to be inadequate. An innovative approach integrating fluorescence scanning cytometry, real-time image analysis, and laser-induced necrosis is described here. Phase I studies with antibody-labeled tumor cell lines demonstrated sensitive fluorescent detection, and subsequent specific killing with a short laser pulse. Phase II studies are proposed to complete development of the clinical-scale PhotosisTM instrument and further develop the antibodies and disposables required for clinical trials. This approach of scanning an entire transplant, thereby locating and killing every detectable tumor cell, provides a unique opportunity to evaluate the efficacy of purging in a setting where information on total tumor burden within the transplant is generated, down to the level of one detectable cell within the transplant. Although this proposal describes a tumor purging application, there are numerous other research and clinical applications that will be enabled once the instrument is completed. PROPOSED COMMERCIAL APPLICATION: These studies will lead to commercialization of a method to eliminate detectable tumor cells from an HSC transplant within a several hour automated procedure. In 1997, over 45,000 HSC transplants were performed worldwide, and the number is increasing 20-25% per year. The resulting instrumentation could ultimately be applicable to any process that requires a highly defined cell product.